Piling system

ABSTRACT

The apparatus comprises a hollow casting tube sealed near its lower end by a plate so that the pile driving hammer can be applied direct to the plate to force the tube into the ground. Cement-sand grout is passed to the space beneath the plate via a pipe passing externally of the casting tube whilst the tube is simultaneously lifted out of the ground.

Unite States atet 1191 Pan Chen 1451 Mar. 11, 1975 1 PILING SYSTEM [76]Inventor: Paul Chuan Pao Chen, 3 Barbecue Garden, 17 Milestone, CastlePeak Rd., New Territories, Hong Kong [22] Filed: Nov. 26, 1973 21 Appl.No.: 419,199

[52] US. Cl. 61/53.64, 61/535 [51] Int. Cl E02d 5/36 [58] Field ofSearch 61/53.6, 53.62, 53.64,

[56] References Cited UNITED STATES PATENTS 2,649,694 8/1953 Pickman61/5364 3,568,452 3/1971 Stifler, Jr, 61/536 Primary Examiner--JacobShapiro Attorney, Agent, or FirmWenderoth, Lind & Ponack [57] ABSTRACT 7Claims, 8 Drawing Figures T' fi 41 K B1\\\/ 3% I ,1- 1 1 6 x, X116PATENTED MAR] 11975 SHEET 2 0f 2 LE m 3m y= y F Q m C 5 FILING SYSTEMThe present invention relates to a method and apparatus for casting asubterranean concrete pile.

In accordance with one aspect of the invention there is providedapparatus for casting a subterranean concrete pile, said apparatuscomprising a tube for sinking into a ground formation in which the pileis to be cast, a sealing member extending internally across the tube ata position adjacent one end thereof and a releasable end plug forclosing said one end of the tube to form a chamber for receivingcement-sand grout and conduit means positioned externally of the tubefor passing the grout under pressure from ground surface into thechamber.

In use of the apparatus the tube is driven into the ground by meansof ahammer, with that end of the tube which is closed by the end plug beingthe lower end. If desired the end plug may be formed with a pointedshape so as to assist entry into the ground for mation. The apparatus ofthe invention has the advan* tage that the interior of the tube isunobstructed so that the driving hammer can be placed within the tube.

In accordance with a further aspect of the invention there is provided amethod of forming a subterranean concrete pile, said method comprisingthe steps of sinking a tube to the ground formation in which the pile isto be cast by applying hammer blows to a sealing member extendinginternally across said tube to seal a lower end thereof, and passing acement-sand grout under pressure into the space beneath said sealingmember by means of a conduit positioned externally of the tube, whilstsimultaneously raising the tube so as ti fill the bore formed by thesinking of the tube.

This method of operation allowed by the apparatus of the presentinvention has two distinct advantages:

Firstly, since substantially all the force of the hammer is applied onlyto the sealing member, it is only necessary for the lower part of thetube and the sealing member to be sufficiently strong to withstand theforce of the hammer. The upper part of the tube may be formed by anumber of separate tubes of much lighter construction. These upper tubesare stacked one upon the other to line the hole left by the castingapparatus as it is sunk into the ground formation.

The second advantage of the above method of operation arises by virtueof the fact that it is now possible, if desired, to halt thesimultaneous passage of grout into the bore and raising of the tube atsome intermediate position, whereupon hammering may be resumed to forcethe tube back into the ground a predetermined distance. This being done,the hammering is stopped and the operationof simultaneously passinggrout into the bore and raising the tube is resumed. The effect of theresumed hammering is to form an enlarged bottom end to the pile, afeature which has advantages to be discussed hereinafter.

In a preferred embodiment of the invention said one end of said tube issecurely fitted with an annular member, said end plug being adapted toclose the aperture left by the annular member to form said chamber.

The end plug is preferably constructed such that, whilst beingreleasable to allow cement-sand grout out of the chamber, it is notcompletely detachable from the remainder of the apparatus. If this isnot done the end plug remains at the bottom of the pile and is notrecoverable.

In order that the invention may be better understood an embodimentthereof will now be described by way of example only and with referenceto the accompanying drawings in which:

FIG. 1 is a cross-sectional side elevation of an apparatus according tothe invention in which the end plug is in place;

FIG. 2 is a view similar to FIG. 1 in which the end plug is released toallow grout out of the chamber; and

FIGS. 3 to 8 illustrate a typical sequence of pile forming operationsperformed with the apparatus of the present invention.

Referring to FIGS. 1 and 2 the casting apparatus comprises a heavycasting tube 1, for example of steel. near to the lower end of which issecurely welded a plate 2 which can also be of steel. Plate 2 serves twopurposes first that of a sealing member in order to seal off the lowerend of the tube l and second that of an anvil for receiving the blows ofa hammer (not shown) whilst the apparatus is being driven into theground. For this reason the casting tube 1 and especially the plate 2must be of strong heavy construction. The casting tube may be formed inany length convenient to the construction and correct operation of theapparatus. It is not necessary for the tube to be of such a length thatit completely leaves the hole left by the apparatus as it is driven intothe ground. For this purpose, separate tubes (not shown) of equaloutside diameter are stacked upon tube 1 as the apparatus sinks into theground. Since very little strain is placed upon them these latter tubesmay be of much lighter c0nstruction.

The end of the tube 1 is securely fitted with an annular member 3 whichforms a seating for an end plug 4. Plug 4 comprises a lower end portion5 and an upwardly extending pillar 6. As seen from FIGS. 1 and 2, pillar6 is of tubular construction for most of its length, opposite sides ofthe tubular part being formed with elongate apertures 7 extendinglongitudinally of the pillar. These apertures 7 are designed toco-operate with a retaining rod 8 which passes through the wall of tube1 and through annular member 3. In this way, end plug 4 is movablebetween the position shown in FIG. 1 in which the bottom end of the tube1 is completely sealed off to form a chamber 9, and the position shownin FIG. 2 in which the end plug is released to allow the contents ofchamber 9 to escape downwardly.

The external surface of end portion 5 and the annular member 3 isshaped, for example conically as shown, to facilitate passage in theground.

The cement-sand grout or other suitable material for forming the pile ispassed into chamber 9 from above ground by means of a supply pipe 10which passes alongside tube 1 and turns at its lower end through thewall of tube 1 into the chamber and is provided with a non-return valve11. Valve 11 may be of any known construction, for example a simple balland spring type as shown. A shoulder 12 is formed as a projection on theside of tube 1 in order to protect the supply pipe from damage duringsinking of the apparatus into the ground.

The method of operation of the apparatus is shown as a sequence in FIGS.3 to 8 and is as follows:

The Figures show diagrammatically the method of forming a vertical pile.Ground level is indicated by reference numeral 13.

The casting apparatus is first driven into the ground to the requireddepth by means of an internal hammer 14 (see FIG. 3). During thisoperation the end plug 4 is closed as shown in FIG. 1, the force of thehammering serving to provide a tight'seal to prevent entry of groundmaterial into chamber 9. As the apparatus sinks into the ground, furthertubes are added on top of tube 1 in order to line the bore produced bythe apparatus.

When the apparatus has reached the required depth cement-sand grout isinjected under pressure via supply pipe 10 into chamber 9 whilst theapparatus is simultaneously raised. The end plug 4 is forced open to theposition shown in FIG. 2 to allow grout 16 to escape from the chamber(see FIG. 4). As the apparatus is raised still further the grout fillsup the space left beneath the apparatus the plate 2 serving to preventescape of grout up tube 1 (see FIG. 5).

The raising of the apparatus may be performed with the winch of the pilerig (not shown) through a multiport tackle arrangement acting on liftinglugs (not shown) provided on the top of tube 1. In this way the uppertube lining sections are pushed upwards, which operation is facilitatedby their lighter construction.

If desired the raising operation may be halted, for example at theposition shown in FIG. 5 whereupon the lifting tackle is disengaged andthe hammer 14 made ready for redriving. The apparatus is then drivendownwards by means of the hammer. This has the effect of forming anenlarged base 17 for the pile (see FIGS. 6 to 8) as well as increasingstill further ground penetration of the grout. During this operationgrout flow in the reverse direction is prevented by the valve 11.

The formation of an enlarged base increases the end bearing value of thepile and thus the ultimate bearing capacity. The ultimate bearingcapacity is also dependent upon the frictional resistance between thepile and the surrounding ground. This frictional resistance is alreadyhigh by virtue of the increased ground penetration of the grout broughtabout by supplying the grout under pressure. However, as mentioned abovethe operation of forming an enlarged base by hammering increases stillfurther ground penetration of the grout, and hence the frictionalresistance between pile and ground.

The ability to form an enlarged base in this way is one of the principaladvantages of the apparatus of this invention, and arises from the factthat the interior of the tube 1 is unobstructed, allowing the hammer tooperate within the tube directly on the casting apparatus rather thanthrough the intermediary of the upper tube linings.

After forming the enlarged base the apparatus is raised again in thenormal manner while simultaneously applying grout under pressure. Theapparatus is raised at a rate which is calculated to maintain apredetermined pressure beneath the plate 2 so that lateral compaction ofthe ground surrounding the pile is effected.

As the apparatus reaches ground level the grouting pressure is graduallyreduced to prevent excessive penetration of the grout into the groundnear the surface (see FIG. 7).

When the apparatus has been completely withdrawn a steel reinforcementcage 18 may be lowered into the grout and held in position as shown inFIG. 8.

If desired a layer of coarse sand or other material may be placed on topof plate 2 during hammering to reduce the noise created by a directmetal to metal contact. However, since the hammering is mostly doneunderground, noise is not much of a problem.

I claim:

1. Apparatus for casting a subterranean concrete pile, said apparatuscomprising a tube for sinking into a ground formation in which the pileis to be cast, an immovable sealing member extending internally acrossthe tube at a position adjacent one end thereof and adapted to receivehammer blows of a pile driver, a releasable end plug for closing saidone end of the tube to form a chamber for receiving cement-sand groutand conduit means positioned externally of the tube for passing thegrout under pressure from ground surface into the chamber.

2. Apparatus as claimed in claim 1 wherein said one end of said tube issecurely fitted with an annular member, said end plug being adapted toclose the aperture left by the annular member to form said chamber.

3. Apparatus as claimed in claim 2wherein said end plug is fitted with ahollow cylindrical extension which is sized to be slidable within theaperture left by the annular member, said extension being open at itsupper end and having openings adjacent its lower end so that grout maypass through the extension to form the pile.

4. Apparatus as claimed in claim 3 wherein said extension has twooppositely disposed elongate apertures each extending along a generatorthereof, and wherein said one end of the tube is further fitted with atansversely extending retaining rod, which rod passes through theaperture left by the annular member, and said two elongate aperturesformed in the end cap extension to thereby limit the movement of the endcap relative to the tube.

5. Apparatus as claimed in claim 1 wherein the lower end of said conduitmeans is provided with a one-way valve to prevent backflow of grout fromthe chamber.

6. Apparatus as claimed in claim 1 wherein said conduit means includes agrout supply pipe which is positioned against the external surface ofthe tube and extends along the tube to a position just beyond saidsealing member whereupon the pipe passes through the tube wall and intosaid chamber.

7. Apparatus as claimed in claim 6 wherein an extension is formed on thewall of the tube at a position just below the position at which the pipepasses through the tube'wall to protect the end of the pipe from damageas the tube is sunk into the ground formation.

1. Apparatus for casting a subterranean concrete pile, said apparatuscomprising a tube for sinking into a ground formation in which the pileis to be cast, an immovable sealing member extending internally acrossthe tube at a position adjacent one end thereof and adapted to receivehammer blows of a pile driver, a releasable end plug for closing saidone end of the tube to form a chamber for receiving cement-sand groutand conduit means positioned externally of the tube for passing thegrout under pressure from ground surface into the chamber.
 1. Apparatusfor casting a subterranean concrete pile, said apparatus comprising atube for sinking into a ground formation in which the pile is to becast, an immovable sealing member extending internally across the tubeat a position adjacent one end thereof and adapted to receive hammerblows of a pile driver, a releasable end plug for closing said one endof the tube to form a chamber for receiving cement-sand grout andconduit means positioned externally of the tube for passing the groutunder pressure from ground surface into the chamber.
 2. Apparatus asclaimed in claim 1 wherein said one end of said tube is securely fittedwith an annular member, said end plug being adapted to close theaperture left by the annular member to form said chamber.
 3. Apparatusas claimed in claim 2 wherein said end plug is fitted with a hollowcylindrical extension whIch is sized to be slidable within the apertureleft by the annular member, said extension being open at its upper endand having openings adjacent its lower end so that grout may passthrough the extension to form the pile.
 4. Apparatus as claimed in claim3 wherein said extension has two oppositely disposed elongate apertureseach extending along a generator thereof, and wherein said one end ofthe tube is further fitted with a tansversely extending retaining rod,which rod passes through the aperture left by the annular member, andsaid two elongate apertures formed in the end cap extension to therebylimit the movement of the end cap relative to the tube.
 5. Apparatus asclaimed in claim 1 wherein the lower end of said conduit means isprovided with a one-way valve to prevent backflow of grout from thechamber.
 6. Apparatus as claimed in claim 1 wherein said conduit meansincludes a grout supply pipe which is positioned against the externalsurface of the tube and extends along the tube to a position just beyondsaid sealing member whereupon the pipe passes through the tube wall andinto said chamber.